1. Field of Invention
This invention relates to laminates and foam filled panel products which are rigid and reasonably strong, and more particularly relates to structurally rigid boards of foam which have at least one planar flat side covered with a facing sheet.
2. Prior Art and Other Considerations
The field of foamed core laminated panels is large and well known in commerce. Over the years, flat rigid sheets and continuous webbed flexible sheets have been used to provide one or both facings ("facers") for a foamed core panel.
The facer sheets have been formed of paper, plastic, aluminum foil, other metals, rubber, wood, and even vegetable based skins. These facer sheets contain cellular plastic foam between two facers in parallel planes in a panel, and form a laminated "sandwich board" configuration.
One of the most successful facer panels has been made using a mat of 100% glass fibers. The glass fibers are bonded together with resin binders to form opposing facers for containing or sandwiching thermosetting plastic foam therebetween.
Another prior art practice has been to pre-attach fiberglass mat or skrim with paper, or plastic, or aluminum foil, or a combination of any two or three.
Glass mats have been saturated with asphaltic materials to form facers of reduced porosity. Multi-layered, pre-assembled, facing sheets of myriad components have also been employed by producers of structural foam core laminate panels.
For many years now, glass fibers having a diameter of 10 microns or less and usually less than 0.5 inches in length, called "micro-fibers" or "fibrous glass dust", have functioned as fillers in the production of glass fiber mats. The function of a "filler" in the manufacture of glass fiber mat sheets, is to decrease the porosity of the fibrous sheet. If the glass fiber sheet has a high porosity, it cannot be used as a facing sheet for thermosetting plastic foams, because the liquid polymer will not be contained by a porous glass fiber mat (sheet). Consequently, the makers of glass fibrous mats have resorted either to a multi-layered facer or to the use of micro-fibers as their best means to accomplish the necessary low porosity of their glass mat so it can be used as a facing material for thermosetting plastic foam laminated panels.
One major problem always confronting the panel users, and thus the producers, of foam core panels has been the safety factor. In recent years, scientists have classified "micro-fibers" as a serious hazard to human safety. These, short, thin glass fibers may ultimately be classified as a human carcinogen. In 1990, The American Conference of Governmental Industrial Hygienists (ACGIH) listed the Threshold Limit Value (TLV) of Fibrous Glass Dust to have a maximum Time Weighted Average (TWA) exposure of only 10 milligrams per cubic meter.
An additional area of safety hazard has been the combustibility of foam core laminated panels, especially when asphalt, plastic or cellulose are employed in making the facing sheets. Both metal facing sheets and glass fiber facing sheets offer some measure of fire safety, but both types have been quite expensive. The addition of hazardous glass micro-fibers has also added to the cost of glass fiber facing sheets.
Accordingly, it is an object of the present invention to provide a foam core laminated structural panel having safe and economical facers.
An advantage of the present invention is the provision of foam core laminated structural panels having relatively non-combustible facers.
Another advantage of the present invention is the provision of foam core laminated structural panels having facers which lack micro-fibers.
Yet another advantage of the present invention is the provision of a reduced porosity, predominately glass fiber facing sheet, devoid of micro-fibers or fibrous glass dust, and which prevents the penetration of liquid polymeric plastic foam mixtures.
Another advantage of the present invention is the provision of foam core laminated structural panels having facers which are smoother to the touch than a 100% glass mat.
Yet another advantage of the present invention is the provision of foam core laminated structural panels having facers which are economical and yet which combat combustibility and porosity while improving surface texture.